The monthly interest repayment amount is 4,267 yuan.

Details:

1. According to the information provided, the loan amount is 400,000 yuan, which can be repaid in six months.

2. The interest is 1.28. We need to calculate the monthly interest repayment amount.

3. Multiply the loan amount by the interest rate (1.28), and the monthly interest amount is 400,000 × 1.28 = 5,120 yuan.

4. Finally, divide the total interest amount (5,120 yuan) by the number of repayment periods (6 months), and the monthly interest repayment amount is 5,120 yuan ÷ 6 Month ≈ 4,267 yuan.

Summary:

According to the conditions of loan amount of 400,000 yuan, repayment in six months, and interest of 1.28, the monthly interest repayment amount is approximately 4,267 Yuan.

Extended information:

Loan installment refers to spreading the loan amount into multiple months for repayment and paying additional interest. In this case, the borrower needs to repay a portion of the principal and interest every month according to the agreed interest rate and repayment period. The interest repayment amount is calculated based on the borrowed amount and interest rate, and usually decreases as the repayment period lengthens, because the principal will gradually decrease, thereby reducing the basis for calculating interest.